LOS ANGELES – A Southern California man whose body was found alongside his girlfriend's after a nearly three-month search is believed to have killed her and then himself in Joshua Tree National Park, authorities said Friday.

Rachel Nguyen, right, and Joseph Orbeso are seen in photos posted to a fundraising page.

Joseph Orbeso fatally shot 20-year-old Rachel Nguyen then shot himself during a hike in the national park in July, according to San Bernardino County Sheriff's Department detectives.

After announcing those findings Friday morning, the Sheriff's Department, later in the day, offered further information that suggests the couple could have indeed gotten lost on the hike, as suspected during the lengthy search for them.

The couple was found under a tree and had positioned their clothing to cover their extremities and protect them from the sun, the Sheriff's Department said.

"It appears they had been rationing their food and had no water," the department said in an updated news release.

Orbeso and Nguyen were reported missing on July 28 when they did not check out of their Airbnb as scheduled. Their vehicle, a burgundy Lexus, was found later that day in the vicinity of the Maze Loop, a popular trail, near the park’s west entrance, officials said.

The Orange County couple planned a trip to the park to celebrate Nguyen's birthday, according to Nguyen's uncle.

A large-scale, nine-day search for the couple was launched with over 250 search and rescue members, aircraft teams and canine units looking for the pair. A spokesman for the park told KTLA at the time of the incident that there was no reason to suspect foul play and officials believed the couple had gotten lost in the park.

Some 2 1/2 months later, hikers found the bodies in a remote area of the park on the morning of Oct. 15.

"Due to suspicious circumstances and visible injuries to the decedents, detectives from the Specialized Investigations Division – Homicide Detail were requested to respond to the location," the Sheriff's Department said in a news release Friday.

Due to loss of daylight, the bodies were not recovered until Monday, Oct. 16. Authorities identified the bodies as Orbeso and Nguyen between Wednesday and Thursday.

Autopsies revealed injuries consistent with a gunshot wound on both bodies, the release stated.

"Based on evidence located at the scene, detectives believe Orbeso shot Nguyen, then shot himself," the Sheriff's Department said. "The investigation into Orbeso’s actions remain under investigation."

The gun found near the bodies was registered to Orbeso, the Sheriff's Department said.

The Sheriff’s Department on Friday said Orbeso was 22, but previous reporting indicates he was 21.